Some modern automobiles have engine oil monitoring systems. These systems provide the user or technician with an indication of when an oil change is needed. The indication is typically provided by illuminating a light or presenting a message to the customer when the system determines that it is time to change the oil.
The engine oil monitoring systems make determinations related to oil life based on variables such as an amount of time, or miles driven, since a last oil change, with the assumption that the oil degrades by an average amount with time and miles. Estimating degradation based on time and/or miles alone has inherent inaccuracies because the degradation depends on many other factors including a quality or health of the engine in which the oil is used, ambient temperature in which the vehicle is being used (e.g., winter-like temperatures as compared to spring or summer-type temperatures), and a type of driving that the car has been used for. Regarding the latter, oil will degrade differently, and generally at an overall higher rate, in a car driven mostly or completely in stop-and-go, or city, driving, than in the same car used mostly for highway driving.
One option for obtaining a better estimate of oil degradation is to analyze the oil to determine a present value of multiple key oil properties. This analysis, though, would require adding relevant sensors, corresponding software, and possibly additional hardware beyond the new sensors to the vehicle, requiring more packaging space for the engine oil life processes and adding weight and cost to the vehicle.
There is a need for technology that can better estimate oil degradation by considering dilution of the oil by one or more unwanted fluids, such as fuel and water, and more particularly to the healing effect that occasional longer trips have on the unwanted dilution.